Investment Securities - Investment Securities Held to Maturity (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 36,747	$ 37,022
Unrealized Losses Recorded in AOCI	(244)	(251)
Carrying Value	36,503	36,771
Gross Unrealized Gains	658	314
Gross Unrealized Losses	(206)	(466)
Fair Value	36,955	36,619
RMBS, Agency
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	32,899	33,299
Unrealized Losses Recorded in AOCI	(231)	(238)
Carrying Value	32,668	33,061
Gross Unrealized Gains	608	293
Gross Unrealized Losses	(169)	(377)
Fair Value	33,107	32,977
CMBS, Agency
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3,848	3,723
Unrealized Losses Recorded in AOCI	(13)	(13)
Carrying Value	3,835	3,710
Gross Unrealized Gains	50	21
Gross Unrealized Losses	(37)	(89)
Fair Value	$ 3,848	$ 3,642

Debt securities, Held-to-maturities, Amortized cost excluding AOCI transfer mark

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Unrealized losses recorded in AOCI on held to maturity securities.

+ References

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Amount of investment in debt security measured at amortized cost (held-to-maturity).

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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